Convert `m nothing` to soong

So that it works in soong-only builds.

Fixes: 388095162
Test: m --soong-only nothing
Change-Id: I9b8b9f4f3b95524cd526476f1141d920011cd47a
diff --git a/android/Android.bp b/android/Android.bp
index bb16856..d27a8fa 100644
--- a/android/Android.bp
+++ b/android/Android.bp
@@ -79,6 +79,7 @@
         "namespace.go",
         "neverallow.go",
         "ninja_deps.go",
+        "nothing.go",
         "notices.go",
         "onceper.go",
         "override_module.go",